4.4 Entity Relationship Diagram

This diagram represents a Version of a entity relationship diagram. It shows this through Invoice that has such features as customers key, product code, date, etc.
We also see the Customer section on this Entity relationship diagram. Customers are instrumental to a company's success so this particular company focused in on inserting their customers basic info into their system.
Which we can then relate customer to product by seeing what that particular customer purchased in the past giving that company the ability to relate through a type of key system.